This group is studying the problem of how organisms sense a change in their environment and transduce the environmental signal into a change in gene expression and morphology. It was found that OxyR, a regulator of hydrogen peroxide-inducible genes in bacteria, is both the sensor and transducer of an oxidative stress signal. Oxidation of the OxyR protein beings about a conformational change which allows OxyR to activate transcription of defense genes. This group has also begun to study how Arabidopsis plants respond to light. Mutants that are no longer responsive to blue light are being isolated in order to define components in the blue light signal transduction pathway.